In recent years, due to growing environmental consciousness, the demand for solventless painting, alternatives to plating and the like is growing in building materials, automotive component parts, cellular phones, electrical machinery products, and the like, and therefore, introduction of a decorating method that uses a film is progressing.
As a polyester film for molding which is used in such a decorating method, various films have been proposed. For example, a polyester film for molding of which a specific molding stress at normal temperature is defined has been proposed (see, e.g., Japanese Patent Application Publication No. 2001-347565).
Furthermore, a polyester film for molding of which a molding stress and a storage elastic modulus at a specific temperature are defined has also been proposed (see, e.g., Japanese Patent Application Publication No. 2005-290354).
Further, a polyester film for molding of which a storage elastic modulus over a wide temperature range is defined has also been proposed (see, e.g., Japanese Patent Application Publication No. 2008-162220).
However, as for the film described in the Japanese Patent Application Publication No. 2001-347565, moldability is not necessarily sufficient, and dimensional stability is not designed by considering the use into which the film is put.
Furthermore, the film described in the Japanese Patent Application Publication No. 2005-290354 has a problem that in a molding method that requires molding at high temperature (around 180° C.), the storage elastic modulus at the time of molding becomes too low, resulting in decline in quality level, such as the roughening of a film surface and the like.
Furthermore, the film described in the Japanese Patent Application Publication No. 2008-162220 exhibits low storage elastic modulus over a wide temperature range and therefore is excellent in moldability. However, the storage elastic modulus in a high temperature region is low so that securing a quality level after molding is not sufficient and satisfactory characteristic in heat resistance is not exhibited.
It could therefore be helpful to provide a biaxially oriented polyester film for molding excellent in moldability, dimensional stability, heat resistance, and post-molding quality level, and is capable of being subjected to a molding process to be suitably used for various molded members.